Recently, as semiconductor integrated circuits have become more highly integrated and their speed of operation has become higher, metal lines in a semiconductor device have become narrower and multi-layered. As the widths of the metal lines become narrower, the resistance and capacitance of the metal lines increase, thereby causing signal delay. Therefore, copper, a metal having low resistance, is used as a material for forming the metal lines to decrease this signal delay.
However, since copper is difficult to etch, copper metal lines are usually fabricated by a damascene process in which copper is first filled in a trench formed on a substrate and then planarized via chemical mechanical polishing.
Such a conventional method of manufacturing a semiconductor device using the damascene process may be summarized as follows.
As shown in FIG. 1, an interlayer insulating layer 12 is first formed on a substrate 10. A trench T is then formed in the interlayer insulating layer 12 by a selective etching process. Subsequently, a copper layer 14A is formed such that the trench T is filled thereby.
As shown in FIG. 2, a copper line 14 may be formed by applying chemical mechanical polishing to the copper layer 14A to confine the copper to the trench T.
However, after the chemical mechanical polishing, a serration shape may be formed on a surface of the copper line, which may cause a short circuit between adjacent copper lines such as is shown in the example of FIG. 2. Therefore, as a result of employing such a conventional method, reliability and yield of the manufactured semiconductor devices may be deteriorated.
To clarify multiple layers and regions, the thickness of the layers are enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part (e.g., a layer, film, area, or plate) is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts.